A method for small scale time increased bandwidth assignment to increase optical network unit ONU downstream energy efficiency includes splitting of downstream scheduling cycles into multiple rounds, using selective ones of the multiple rounds as probing rounds and other than said selective ones of the multiple rounds as fixed rounds, the probing rounds and fixed rounds being cooperatively selected for energy efficiency without limitations in length of the downstream scheduling cycles.
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1. A method for small scale time increased bandwidth assignment to increase optical network unit ONU downstream energy efficiency, said method comprising the steps of:
a. splitting of downstream scheduling cycles into multiple rounds at an optical line terminal (OLT), comprising:
i) splitting each downstream scheduling cycle into one probing round followed by fixed rounds, splitting a grant calculated from a whole scheduling cycle k into R equal parts and sending the calculated grant in R rounds and regular intervals; and
b. using selected ones of said multiple rounds as probing rounds and other than said selected ones of said multiple rounds as fixed rounds, said probing rounds and fixed rounds being cooperatively selected for energy efficiency without limitations in length of said downstream scheduling cycles, wherein said probing rounds represent a transmission, to ONUs in a network, of information comprising a respective transmission duration and interval between consecutive transmissions for each ONU.
2. The method of
ii) monitoring by an ONU downstream medium access control MAC during said probing round a transmission duration destined to it and an interval between two consecutive transmissions.
3. The method of
iii) using calculated grant values to receive data for a known duration and switching its receiver to a sleep mode.
4. The method of
iv) an optical line terminal OLT downstream MAC, after end of an Rth transmission, polling all ONUs downstream queues and decides again on upcoming cycle downstream timeslot durations for each of them.
5. The method of
6. The method of
7. The method of
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This application claims priority to provisional application No. 61/543,374 filed Oct. 5, 2011, the contents thereof are incorporated herein by reference
The present invention relates generally to optical communications, and more particularly, to 802.3av compliant method using small timescale bandwidth assignment for increased optical network unit ONU downstream energy efficiency.
Energy efficient networking has become a key requirement in recent years. The main factors contributing to this need are the reduction of the global carbon footprint but also the reduction of network operational expenditures (OPEX). Moreover, regulators worldwide are beginning to mandate compliance with specific energy consumption figures. For these reasons, novel technological solutions are being sought to minimize energy consumption at various layers, ranging from the physical layer up to the higher ones. Although Passive Optical Networks (PON) are inherently more energy-efficient than other types of access networks due to their use of a passive network infrastructure as shown in
A fixed bandwidth allocation (FBA) scheme has been proposed by others to achieve ONU downstream energy efficiency.
The main downside of the previously proposed FBA scheme (
An alternative scheme proposed by others does not use a fixed downstream cycle duration. The exact duration is determined dynamically by the data in the downstream ONU queues and the scheme used for downstream grant sizing. This scheme aims at improving downstream energy efficiency by ensuring that the OLT will never use a downstream scheduling cycle shorter than a given value each time. This value for cycle k is determined for ONU i as ρ·Δk−1(i), where ρ is a system parameter, known to the OLT and all ONUs. Each ONU therefore has to constantly monitor Δk (i) and accordingly set its Rx to sleep mode for a duration equal to ρ·Δk(i) in the next cycle. The OLT on the other hand has to take care not to schedule the next transmission for the ONU sooner than ρ·Δk(i) (it can though be scheduled later than that depending on the traffic of other ONUs). In the next cycle, a new interval Δk+1(i) will be decided based on the data in the rest of the ONUs' queues. In addition, it is crucial that the OLT transmits downstream GATE messages to an ONU only after the transmission of data; otherwise it would be impossible for the ONU to go to sleep without missing some grants.
An example of the alternative scheme of is shown in
Accordingly, there is a need for solving the problem of ONU-side energy efficient downstream operation with a method that provides a better energy-efficiency/QoS trade-off.
The present invention is directed a method for small scale time increased bandwidth assignment to increase optical network unit ONU downstream energy efficiency. The method includes splitting of downstream scheduling cycles into multiple rounds, using selective ones of the multiple rounds as probing rounds and other than said selective ones of the multiple rounds as fixed rounds, the probing rounds and fixed rounds being cooperatively selected for energy efficiency without limitations in length of the downstream scheduling cycles.
These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings.
The present invention is directed an inventive method for downstream scheduling which allows the ONUs to be able to determine the downstream timeslots during which they can set their Rx to the sleep mode, while performing dynamic downstream bandwidth allocation. The method is adjustable to provide the required trade-off between energy-efficiency and QoS performance.
From the foregoing it can be appreciated that the inventive method enables significant energy efficiency benefits without modifying the existing 10G-EPON protocol. In addition, the average energy savings achieved by the inventive method are independent of the average network load and the traffic patterns. Thus, it allows for easier control over the parameters to achieve the required QoS performance versus energy savings trade-off.
This invention introduces a Small Timescale Fixed Bandwidth Allocation (STFBA) procedure to achieve downstream energy efficiency combined with scheduling dynamicity. The main idea behind STFBA is that it operates similarly to FBA, but only during limited durations. In that way, it can both leverage on the energy savings potential of FBA but also manage to efficiently handle traffic fluctuations in a dynamic manner. In addition, the energy savings versus QoS performance trade-off can be controlled much more easily than the above alternative method discussed above.
The operation of the proposed STFBA is as follows: although the OLT maintains the concept of downstream cycles intact, the way grant sizing is performed is modified. As shown in
The inventive downstream MAC (500) aspect of an ONU (400) under the STFBA scheme is described as a block flow diagram in
It is noted that while a very large number of rounds per cycle (hence very short durations) would result in energy savings approaching those of FBA, this would also lead to increased network underutilization due to the requirement for the OLT side to transmit integral Ethernet frames during each round.
The ONU downstream MAC (500) monitors during probing round the transmission duration destined to it (501), and the interval (502) between two consecutive transmissions. Then uses the calculated values to receive data for a known duration (504) and then safely switch its Rx (402) to the sleep mode (505) 620. Traffic fluctuations are handled efficiently in a dynamic manner 621 and the concept of downstream scheduling cycles is kept intact 622. The exact grant sizing for the whole cycle can be decided based on any of the schemes proposed in the prior art literature noted above 623. A GATE message and request for REPORT only sent to each ONU once every downstream scheduling cycle, during the probing round (208) 624.
After the end of the Rth transmission, the OLT downstream MAC (200) polls all ONU downstream queues (201) and decides again on the upcoming cycle downstream timeslot durations for each of them (202) 630.
The foregoing is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that those skilled in the art may implement various modifications without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention.
Zhang, Jingjing, Kanonakis, Konstantinos, Cvijetic, Neda
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